A somewhat derogatory way of referring to a female who is immediately available for sex. It can be qualified to give a more accurate description of the female in question e.g. “a nice bit of rumpo” would be a female who is attractive as well as available, while “a right bit of old rumpo” would be a female who is available to anyone and his dog.
Used often by pre-teen girls on twitter, "Mother Rumpin" is often used as a way of saying "mother fucking" or more literally "I'm scared to swear on twitter because my parents insist on following me." Often used while tweeting the pope, can be directly translated into latin as Mater Caudam. Girls who use this expression often have a liking for furry animals such as dogs.
@liz_gardener: Ain't nobody fresher than the Mother Rumpin pope